This invention relates to processes for generating thiocyanatoalkyltrialkoxysilanes and preferably thiocyanatopropyltriethoxysilane.
Thiocyanatopropyltriethoxysilane is used by the rubber industry as a reinforcement agent. The EtO-groups of this silane compound show reactivity towards the OH-groups of fillers (e.g., precipitated silicas), while the SCN-group (in combination with accelerators and sulfur) reacts within the polymer. Stable bonds form, therefore, between fillers and polymer via the silane.
Thiocyanatopropyltriethoxysilane is produced by reacting chloropropyltriethoxysilane and sodium thiocyanate in ethanolic solution under elevated pressure. The typical reaction involving known reagents proceeds as follows: EQU (EtO).sub.3 Si--(CH.sub.2).sub.3 --Cl+NaSCN.fwdarw.(EtO).sub.3 Si--(CH.sub.2).sub.3 SCN+NaCl
Salt generated by this reaction is removed in a centrifuge immediately after the reaction. The resulting filter cake of salt is washed with ethanol and, according to the previously employed process, this wash ethanol is then mixed with the filtrate resulting from the centrifugation step. The resulting mixture is distilled and the substance is freed of the ethanol.
One of the problems with the previously employed process is the length of time it takes to distill the ethanol. Thus, it would be advantageous to the industry if the efficiency of the method could be improved by shortening the distillation time. Due to precipitation of solids previously dissolved in the ethanol as a result of the distillation step, another solid removal step must follow. Therefore, it would also be an advantage to the industry if the subsequent solid removal step could be eliminated.